Introduction: Giant Backlit LED Skull Sign

About: We're Jaimie & Jay! We make DIY Halloween projects on YouTube. Helping you make awesome and spooky stuff.💀

We made a huge backlit LED skull sign for our workshop using the X-Carve and an Arduino!

A few weeks ago we helped a friend out and used our X-Carve to make a big sign for an event. We got inspired and realized we didn’t have a sign of our own so we set out to design it! We used birch plywood and built it in two layers, then used an Arduino to control the LED strips that light it up. This was a relatively simple project that was as much fun as it looks. You should definitely make one!

We recommend watching the video above and following along with the written steps!



Step 1: Prepping the Plywood for Carving

We used 1/2" birch plywood and began by ripping two pieces to 30" wide on the table saw. This is the size our X-Carve can handle so we basically maxed it out. Plywood worked really well for this and has worked well, in general for indoor signs we've made. We considered using a hardwood but since we were going to paint it, plywood was the more economical choice.

We're going to be making two major carves so we needed two pieces of identical size.

To prepare for the CNC cuts, the plywood gets aligned squarely to the bed of the X-Carve and clamped down. As you can see, the sheet just about maxes out our cutting area.

TIP: If you don't have enough space to breakdown a full 4' x 8' sheet of plywood at home, the big box stores will usually break it down into some basic pieces for you, for FREE! (Much easier to get home that way, too.)

Step 2: X-Carving the Back and Front of the Skull

We're using the X-Carve CNC to cut the skull shape, and using a 1/8" spiral down-cut bit because it leaves a perfectly clean finish on the plywood. There are lots of different types of bits you can use, depending on what kind of work you're doing. Whenever possible, we try to use the right bit for the type of cut we want to make.

The first carve is the outer profile of the skull logo and will be painted black. This went without a hitch but we did end up changing the design a bit halfway through, which we'll elude to more later.

Next, we put in the second board and cut the top layer of the Skull, which was 13 individual pieces. This took a little longer but still (luckily) went off without a hitch. So far, so good!

TIP: Using a router to make these cuts by hand instead of a CNC would have worked just as well, it just would have taken a lot longer to do it. If you don't want to do the cuts by hand and want to use a CNC, many major cities now have variations of publicly-accessible workshops and 'maker spaces' with CNC and/or laser cutters that you can access!

Step 3: Cleaning Up the Skull Parts

The X-Carve leaves small tabs so the pieces don't fall out or move when you're doing through-cuts. This helps a lot to keep things in place while doing a cut like this.

Filing off the tabs was easy with a small hand-file and luckily we didn't have any problems on either of the CNC cuts. We DID need to back and redo some cuts later, which we'll get to later, but otherwise things went okay so far.

We couldn't resist doing a dry-fit to check it out. It was already looking AWESOME at this point. We debated just leaving it as is but knew it would look even better with paint.

TIP: Pick up a set of "needle files". They will be your best friend. Here's a set we like:

Step 4: Whitewash Staining the Front Layer of the Skull

The white front layer of the skull got stained with a White Wash pickling stain. We wanted it to be white(ish) but still be able to see the wood grain through the white which is why we didn't just use paint. We applied it with a foam brush, doing one coat on the face and two coats on the end grain.

The White Wash stain is water-based so it goes on and dries quickly so we had to periodically stop and wipe off the pieces as we worked our way through everything.

Staining the front of the large piece was a lot of fun, it looked so cool!

TIP: Whenever you're staining (or painting) have a few different brushes handy and ready to go in case you encounter some small nook and crannies that you're main brush or pad can't access.

Step 5: LEDs? Hmm. Well, Ok! DESIGN CHANGE!

At this point, we were ready to paint the back piece black but realized we wanted to put LEDs on the sign. We originally had planned NOT to do lights/LEDs in order to keep it simple...but we just couldn't resist. We went back and spent loads of time trying to figure out where they should go, how to power them, etc.

In the end we decided to cut circuits into the back piece as well so the light could shine through the back. This meant figuring out a way to re-align the piece we'd already cut on the CNC into the exact same spot so that the circuit cut outs would line up with the ones in the front.

Luckily, we still had the cut offs from the original cut and used those to help align the pieces.

Another trick we found was making the circuits in the back oversized. This gave us a little leeway for placement of the front pieces and also lets more light through!

Because of the weirdness of the setup, some of the cuts didn't go all the way through the plywood so we used needle files again to clean up any spots in the circuits that needed to be deburred.

TIP: Don't be afraid to change your design. Sure, it's more work and sometimes sets you back some time and materials. But looking back, if we hadn't done the LEDs it's hard to imagine this being anywhere near as awesome.

Step 6: Painting the Back! (Finally...)

At long last, we took the back piece outside and used a flat black spray paint (black primer) to paint the entire back.

This was fairly simple, though we did make sure to hit the circuit cut outs from multiple angles to get the paint on the inner edges.

Any spots that were missed we hit with black acrylic paint and a small brush.

TIP: Don't use spray paint in the wind. Bad idea. Also, don't use it inside with no ventilation. Also a bad idea!

Step 7: The "Middle Layer": Waxed Paper Diffusion!

To further add to the complication of the project, we decided in order to properly diffuse the LED lights we needed something across the open circuits. We decided on waxed paper.

We sandwiched a sheet of it in between the two layers by first super gluing it to the bottom, then cutting out a ton of small areas that would reveal enough of the black layer that we could still properly attach the white pieces.

This seemed ridiculous when we were doing it but it actually worked perfectly.

TIP: Diffusing your lights will often lead to things looking a lot better! You can use paper, plastic, even paint to help diffuse the brightness of the light and soften things. Think "lampshade".

Step 8: Attaching the Front to the Back

Using the small squares and all of the surface areas we exposed around the paper, we used super glue and attached the white pieces to the base. We planned to sink screws in from the back for permanent attachment but this helped us align things in the meantime.

Once the glue dried, we drilled small pilot holes from the back side and then sunk screws into each piece.

The sign needed to float 1" off the wall to give the LED light enough room to bounce off the wall, so for that, we attached 1" plastic spacers to the back at the four mounting points that we drilled into the front. The mounting holes were placed in inconspicuous places and we later painted black over the screws to hide them.

TIP: Glue doesn't stick all that well to paint. If glue was going to be the permanent solution here we'd have stripped away the black paint so we could get a wood-to-wood surface. Since we were using screws, we didn't bother doing this.

Step 9: The Arduino and the LEDs!

We attached the LEDs to the back by sticking them around the perimeter and then in and around the open circuits. The LED strip doesn't bend well, so in the future, we might go a different direction for this type of setup, but it worked well enough! We also used hot glue periodically to hold down areas that didn't stick as well.

The Arduino (The "Brain")

We used an Arduino Micro for this to control the LEDs that light up the sign. There are lots of off the shelf LED controllers available but we enjoy coding it ourselves. It gives us more control and allows us to change things whenever we want, which is right up our alley! Along with the LEDs (300 sequential LEDs, all in a single strip), there’s the Arduino Micro, a small breadboard, a 100uF capacitor, a 470ohm resistor, and a barrel jack for the 5V power source.

Powering Everything

The Arduino uses a USB micro adapter for its power and the LEDs are powered externally by a separate 5V power adapter. Because there are 300 LEDs and they’ll be using a lot of power, its recommended to power them separately and not through the Arduino. Since both the Arduino and the LEDs use a 5V power source, we could have spliced the one wall adapter to power them both…but in our case, it was easier to just use two cords. We might upgrade it in the future to simplify once we’re sure we’ll stick with this configuration long-term.

A Mini Breadboard?

The LED manufacturer recommends putting a 100-1000uF capacitor on the positive/negative terminals between the power input the LEDs to prevent any surges from damaging the LEDs, so we did that (100uF). Additionally, they recommend putting a 470ohm resistor between the data pin of the LEDs and the Arduino for the same reason, so we did that too. Since we didn’t have a circuit board to solder these extra components to, we used the breadboard as a junction to get the capacitor and resistor in place. We also used it as a junction for the power and ground jumpers, since it was there.

The Code

We’re using FastLED, which is an excellent free library available for Arduino that makes it super simple to make LEDs do…basically whatever you want. You can choose which type of LEDs you’re using and then use some really simple APIs to control them. Highly recommended if you’ve not used it before! Otherwise, the code is dead simple! Choose your LED type, figure out how many there are, then tell them what to do.

If you'd like to see the actual code, check it out here:

TIP: If you don't want to do any of this, you can pick up off-the-shelf LED controllers which are just as awesome. Here's a great example:

Step 10: The Final Results!

We couldn't be happier with how this came out! In the end we were EXTREMELY happy that we went back, changed the design a bit, and added the lights.

Thanks for reading! If you'd like to watch the whole build video, you can find it in Step One above. :)

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